1. Field of the Invention
The present invention relates to a button telephone apparatus (key-system) and an Internet communication system, in particular, those that bidirectionally exchange telephone audio packets between a conventional Internet network (in a narrow sense) and a button telephone apparatus (key-system) through a public telephone network corresponding to the ISDN (Integrated Services Digital network).
2. Description of the Related Art
Conventionally, from a view point of low cost of a long distance communication, as an audio communication network, a system using an Internet network has been developed.
Internet networks are roughly categorized as an Internet network in a broad sense and an Internet network in a narrow sense. In the former Internet network, various networks are connected regardless of their modes. On the other hand, in the later Internet network, with a source of ARPT (Advanced Research Projects Agency) NET, IP (Internet Protocol) is used as a common protocol. The above-described Internet network is categorized as the latter (namely, an Internet network in a narrow sense).
As a first related art reference of an audio communication system using the latter type Internet network, a technology of a service provider that provides the user with a connection service to an Internet network is disclosed as Japanese Patent Laid-Open Publication No. 10-98548. In the first related art reference, the delay time of transmission/reception packets in the Internet network is measured by comparing the transmission time of the packets with the reception time thereof. When the delay exceeds a predetermined time period (in other words, if a call cannot be transmitted through the Internet network due to congestion), as a user service, the service provider informs the user of a message that represents xe2x80x9cSERVICE IS CURRENTLY NOT AVAILABLExe2x80x9d.
As a second related art reference disclosed as Japanese Patent Laid-Open Publication No. 10-164129, a delay time is detected in a similar manner as the first related art reference (Japanese Patent Laid-Open Publication No. 10-98548). In the second related art reference, corresponding to the amount of the delay time, part of received packets are deleted.
In the above-described audio communication system, only the Internet network is used as a communication medium.
In other words, in such related art references, a structure of which the Internet network is used as a new communication network along with the conventional telephone exchange network is not used.
Thus, countermeasures against congestion of the Internet network are required. When the Internet network is used, depending on the congestion thereof, packets cannot be transmitted and received. Alternatively, the data quality of a call may remarkably deteriorate.
Although the above-described related art references disclosed as Japanese Patent Laid-Open Publications Nos. 10-98548 and 10-164129 are technologies against such countermeasures, they do not provide substantial solutions against deterioration of communication environment due to congestion of the network.
In other words, if the user should make an urgent call, the technology of the first related art reference disclosed as Japanese Patent Laid-Open Publication No. 10-98548 does not satisfy the user""s needs. In addition, when the user hears a message xe2x80x9cSERVICE IS CURRENTLY NOT AVAILABLExe2x80x9d, he or she cannot know the thing to do next.
In the second related art reference disclosed as Japanese Patent Laid-Open Publication No. 10-164129, since part of audio data of the user is discarded. In this case, an important part of the audio data may be lost. In other words, the system cannot determine which of part of data is important for the user.
Thus, it cannot be said that such related art references provide the user with sufficient services. In other words, low cost communication has tradeoffs of urgent communication request and important data. Consequently, the user cannot be satisfied with such a service.
To solve such a problem, according to the present invention, a conventional telephone exchange network is still used. In addition, the Internet network can be selectively used. When audio data should be transmitted on real time basis, if it cannot be transmitted through the Internet network, the conventional telephone exchange network that has a stable communication quality is used. Thus, the user""s convenience can be consistent with high quality of data communication.
The present invention is made from the above-described point of view. An object of the present invention is to provide an Internet communication system that allows audio data to be securely to be received and transmitted without a fluctuation of data quality depending on a time zone.
A first aspect of the present invention is an Internet communication system, comprising a plurality of ISDN (Integrated Services Digital network) lines, an Internet network connected to said ISDN lines using IP (Internet Protocol) as a common protocol, at least one button telephone apparatus connected to said ISDN lines, and at least one telephone unit connected to said button telephone apparatus, wherein said button telephone apparatus has a selecting means for selecting a conventional telephone function or an Internet telephone function, wherein when the selecting means selects the Internet telephone function, said button telephone apparatus converts dial data received from said telephone unit into an IP address, the dial data representing a call destination, converts data of the audio signal received from said telephone unit into IP packets, and transmits the IP packets to said Internet network, and wherein when said button telephone apparatus determines that said Internet network of the call destination is in a congestion state, the selecting means selects the conventional telephone function and re-transmits the audio data received from said telephone unit to the same call destination.
A second aspect of the present invention is a button telephone apparatus, connected to at least one telephone unit, for communicating with a plurality of ISDN (Integrated Services Digital network) lines and with an Internet network connected to the ISDN lines with IP (Internet Protocol) as a common protocol, comprising selecting means for selecting a conventional telephone function or an Internet telephone function, wherein when said selecting means selects the Internet telephone function, said button telephone apparatus converts dial data received from said telephone unit into an IP address, the dial data representing a call destination, converts data of the audio signal received from said telephone unit into IP packets, and transmits the IP packets to said Internet network, and wherein when said button telephone apparatus determines that said Internet network of the call destination is in a congestion state, said selecting means selects the conventional telephone function and re-transmits the audio data received from said telephone unit to the same call destination.
In other words, according to the present invention, the button telephone apparatus has two functions that are a conventional telephone function and an Internet telephone function. The user can selectively use one of these functions. When the user uses the Internet telephone function, the apparatus detects the delay of transmitted packets so as to determine whether or not the Internet network congests. When the congestion state of the Internet network exceeds a predetermined level, the apparatus automatically switches the Internet network to a ISDN line exchange network. Corresponding to dial data that was used for the Internet network, the call is re-dialed to the line exchange network. Thus, the audio data of the user can be automatically re-originated.